Mechanical warewashing machines including dishwashers have been common in the institutional and household environments for many years. Such automatic warewashing machines clean dishes using two or more cycles which can include initially a wash cycle followed by a rinse cycle. Such automatic warewashing machines can also utilize other cycles, for example, a soak cycle, a pre-wash cycle, a scrape cycle, additional wash cycles, additional rinse cycles, a sanitizing cycle, and/or a drying cycle. Any of these cycles can be repeated, if desired, and additional cycles can be used. Rinse aids are conventionally used in warewashing applications to promote drying and to prevent the formation of spots.
In order to reduce the formation of spotting, rinse aids have commonly been added to water to form an aqueous rinse that is sprayed on the dishware after cleaning is complete. The precise mechanism through which rinse agents work is not established. One theory holds that the surfactant in the rinse agent is absorbed on the surface at temperatures at or above its cloud point, and thereby reduces the solid-liquid interfacial energy and contact angle. This leads to the formation of a continuous sheet which drains evenly from the surface and minimizes the formation of spots. Generally, high foaming surfactants have cloud points above the temperature of the rinse water, and/or do not exhibit a cloud point, and, according to this theory, would not promote sheet formation, thereby resulting in spots. Moreover, high foaming materials are known to interfere with the operation of warewashing machines.
In some cases, defoaming agents have been used in an attempt to promote the use of high foaming surfactants in rinse aids. In theory, the defoaming agents may include surfactants with a cloud point at or below the temperature of the rinse water, and would thereby precipitate out and modify the air/liquid interface and destabilize the presence of foam that may be created by the high foaming surfactants in the rinse water. However, in many cases, it has been difficult to provide suitable combinations of high foaming surfactants and defoamers to achieve desired results. For example, for certain high foaming surfactants, it has often been necessary to provide defoaming agents that are chemically quite complicated. For example, Published International Patent Application No. WO89/11525 discloses an ethoxylate defoamer agent that is capped with an alkyl residue. Additionally, there are often concerns regarding providing rinse aids that are environmentally friendly, and that include components that are suitable for use in food service industries.
A number of rinse aids are currently known, each having certain advantages and disadvantages. There is an ongoing need for alternative rinse aid compositions.